Bi-Directional Non-Linear Spring

ABSTRACT

A linear spring member having an annular region with a first thickness connected in series by cylindrical regions having a second thickness, wherein the first thickness is less than the second thickness. Outer portions of adjacent annular regions are coupled together by a first cylindrical region and inner portions of adjacent annular regions are coupled together by a second cylindrical region such that the effective spring rate of the bi-directional spring device increases symmetrically as it is displaced in either compression or tension.

RELATED APPLICATIONS

This is a divisional application of U.S. application Ser. No.15/344,434, filed Nov. 4, 2016, entitled “Bi-Directional Non-LinearSpring” which is incorporated by reference in its entirety herein.

GOVERNMENT LICENSE RIGHTS

This invention was made with government support. The government hascertain rights in the invention.

BACKGROUND

Sensors, including optical or electrical sensors, used in vehicles canbe sensitive to vibration which can degrade performance. A suspensionsystem, such as a conventional coil spring, can be used to support asensor in an attempt to minimize transmitted vibration. However, suchsystems can result in large displacements of the sensor during an eventof high acceleration or high deceleration. Likewise, devices maygenerate vibrational forces, including high-amplitude vibration, whichneed to be isolated from sensitive instrumentation. Conventionally, whensensors have been carried by rocket systems, for example, launch locksor bumpers have been used to minimize sensor displacement during alaunch or landing event. However, launch locks are complicated andexpensive and bumpers can result in high impacts to the sensor during anextremely high acceleration or deceleration event. Other systems thatresult in smaller displacements are “stiff” systems that do notadequately attenuate vibration during operation. In other systems,vibrations are attenuated using arrangements that are “stiff” while intension and “soft” while under compression. It is therefore desirable tohave a device that can act as a bi-directional spring with non-linearspring rates that provide for limited displacement in multiple degreesof freedom during high amplitude vibrational events while attenuatinglow level vibration during low vibrational events.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the invention will be apparent from thedetailed description which follows, taken in conjunction with theaccompanying drawings, which together illustrate, by way of example,features of the invention; and, wherein;

FIG. 1 is a perspective view of a bi-directional spring in accordancewith an example of the present disclosure;

FIG. 2 is an exploded perspective view of the bi-directional spring ofFIG. 1;

FIG. 3 is a side view of the bi-directional spring of FIG. 1;

FIG. 4 is a side view of a bi-directional spring in accordance with anexample of the present disclosure;

FIG. 5 is a perspective cross-sectional view of the bi-directionalspring of FIG. 4;

FIG. 6 is a perspective cross-sectional view of a bi-directional springin accordance with one or more examples of the present disclosure;

FIG. 7 is a cross-sectional view of a bi-directional spring coupled to abi-directional non-linear spring in accordance with one or more examplesof the present disclosure;

FIG. 8 is a support platform supported by an arrangement ofbi-directional linear and non-linear springs in accordance with one ormore examples of the present disclosure;

FIG. 9 is the support platform of FIG. 8 carrying a payload inaccordance with one or more examples of the present disclosure;

FIG. 10 is a cross-sectional perspective view of a bi-directional springin accordance with one or more examples of the present disclosure;

FIG. 11 is a cross-sectional side-view of a bi-directional spring inaccordance with one or more examples of the present disclosure;

FIG. 12 is a cross-sectional side-view of a bi-directional spring inaccordance with one or more examples of the present disclosure;

FIG. 13 is a cross-section side-view of a bi-directional spring inaccordance with one or more examples of the present disclosure; and

FIG. 14 is a perspective view of a bi-directional spring in accordancewith one or more examples of the present disclosure.

Reference will now be made to the exemplary embodiments illustrated, andspecific language will be used herein to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended.

DETAILED DESCRIPTION

As used herein, the term “substantially” refers to the complete ornearly complete extent or degree of an action, characteristic, property,state, structure, item, or result. For example, an object that is“substantially” enclosed would mean that the object is either completelyenclosed or nearly completely enclosed. The exact allowable degree ofdeviation from absolute completeness may in some cases depend on thespecific context. However, generally speaking the nearness of completionwill be so as to have the same overall result as if absolute and totalcompletion were obtained. The use of “substantially” is equallyapplicable when used in a negative connotation to refer to the completeor near complete lack of an action, characteristic, property, state,structure, item, or result.

As used herein, “adjacent” refers to the proximity of two structures orelements. Particularly, elements that are identified as being “adjacent”may be either abutting or connected. Such elements may also be near orclose to each other without necessarily contacting each other. The exactdegree of proximity may in some cases depend on the specific context.

An initial overview of technology embodiments is provided below and thenspecific technology embodiments are described in further detail later.This initial summary is intended to aid readers in understanding thetechnology more quickly but is not intended to identify key features oressential features of the technology nor is it intended to limit thescope of the claimed subject matter.

In accordance with an example of the present disclosure, a suspensionsystem having a plurality of struts mounted to a support platform isdisclosed. The suspension system is coupled to a payload. Each strutcomprises a spring strut having a non-linear spring component and alinear spring component. The linear spring has a “linear” or constantspring rate. The non-linear spring rate changes as the spring isdisplaced. The struts are configured to constrain multiple (e.g., atleast two and up to six) degrees of freedom (i.e., independentdirections of motion) of the payload such that the fundamental resonantmodes of the suspension are at closely spaced frequencies. Thenon-linear spring rates of the struts are low when not exposed to largeforces and therefore provide substantial attenuation of anylow-amplitude transmitted vibrational forces. The non-linear springrates of the struts increase as longitudinal forces acting on the strutsincrease which limits displacement of the supported payload when exposedto high amplitude vibrational forces acting on the support platform. Inone aspect, the non-linear spring has a spring rate that increasessymmetrically in compression or tension as a function of displacement.The linear spring can be coupled in series with the non-linear springand a longitudinal axis of the linear spring is aligned to be coaxialwith a longitudinal axis of the nonlinear spring. There are multiplepossible combinations of linear and nonlinear springs which can be usedto assemble the suspension system and achieve the same result. Exemplarysprings are disclosed herein.

In one embodiment, the bi-directional spring comprises a compliantmember, such as a planar circular or a rectangular compliant member. Arigid annular member is disclosed having a uniform thickness andenclosing an outer portion of the compliant member. The compliant membercan be disposed within the rigid annular member, wherein the center ofthe compliant member and the center of the first rigid annular memberare collinear. The compliant member can comprise a thickness less thanthe thickness of the rigid annular member. In one aspect, the compliantmember can be circular. A pair of opposing center constraint members canbe disposed on either side of the compliant member and these can beconcentric with the compliant member and the rigid annular member. Inone aspect, this bi-directional spring can be described as a diaphragmspring. A plurality of such diaphragm springs can be coupled together.

In one embodiment, a system is disclosed that can comprise abi-directional spring member having a variable spring rate mounted to avehicle and carrying a sensor thereon. The bi-directional spring membercan comprise a rigid annular member enclosing a portion of a compliantmember, wherein the thickness of the compliant member can be less thanthe thickness of the rigid annular member. A center portion of the rigidannular member and a center portion of the compliant member can becollinear, wherein an imaginary axis passing through the center portionsof the compliant member and the center of the rigid annular member canbe substantially perpendicular to a face of the compliant member and aface of the rigid annular member. Flexure of the compliant member canaccommodate movement of the sensor during vibrational events fromoperation of the vehicle or operation of a device associated with thevehicle. Of course other-shaped compliant members are contemplatedherein. A linear spring member is coupled to the non-linearbi-directional spring to create an improved spring device capable ofattenuating both low and high amplitude vibrations.

A method of minimizing vibrational forces using the system can compriseusing a vehicle having a bi-directional spring member disposed on thevehicle, the spring member carrying a sensor disposed in a center of thespring member. The bi-directional spring member can comprise a rigidannular member having a first thickness and a compliant member disposedin part within the rigid annular member having a second thickness,wherein the second thickness can be less than the first thickness, andwherein an imaginary axis passing through the center of the compliantmember and the center of the rigid annular member can be substantiallyperpendicular to a face of the compliant member and a face of the rigidannular member. The method can further comprise creating a load on thebi-directional spring by moving the vehicle or operating a deviceonboard the vehicle, causing a force to act on the bi-directional springin a direction that is parallel with the imaginary axis passing throughthe center of the compliant circular planar member and in a directionaway from a position of the sensor. It is understood that the technologyis primarily useful when used in connection with a system of springlinkages and/or a non-linear spring.

In one aspect, the bi-directional nonlinear spring comprises at leasttwo compliant members having a first thickness coupled to connectingrigid annular members having a second thickness. The first thickness isless than the second thickness and the rigid annular membersalternatingly connect either the outer diameter of a compliant member tothe outer diameter of an adjacent compliant member or the inner diameterof a compliant member to the inner diameter of an adjacent compliantmember such that they are structurally connected in series. Theeffective spring rate of the nonlinear spring increases symmetrically asit is displaced in either compression or tension.

It is to be understood that the example inventive concepts andtechnology discussed herein is/are not limited to the particularstructures, process steps, or materials disclosed herein, but areextended to equivalents thereof as would be recognized by thoseordinarily skilled in the arts. It should also be understood thatterminology employed herein is used for the purpose of describingparticular inventive concepts only and is not intended to be limiting.

Reference throughout this specification to “one example” or “an example”means that a particular feature, structure, or characteristic describedin connection with the example is included in at least one example ofthe present invention. Thus, appearances of the phrases “in one example”or “in an example” in various places throughout this specification arenot necessarily all referring to the same example.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary. In addition, various embodiments and examples of the presentinvention may be referred to herein along with alternatives for thevarious components thereof. It is understood that such embodiments,examples, and alternatives are not to be construed as de factoequivalents of one another, but are to be considered as separate andautonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments. In thedescription, numerous specific details are provided, such as examples oflengths, widths, shapes, etc., to provide a thorough understanding ofembodiments of the invention. One skilled in the relevant art willrecognize, however, that the invention can be practiced without one ormore of the specific details, or with other methods, components,materials, etc. In other instances, well-known structures, materials, oroperations are not shown or described in detail to avoid obscuringaspects of the invention.

With reference now to FIGS. 1-3, a bi-directional spring device 5 isdisclosed comprising a compliant member 10 having a uniform thicknessacross the compliant member 10. A first rigid annular member 15 having auniform thickness can be disposed on a first side 11 of the compliantmember 10. A second rigid annular member 16 having a uniform thicknesscan be disposed on a second side 12 of the compliant member 10. Thethickness of the first rigid annular member 15 and the second rigidannular member 16 can be substantially equivalent. In accordance withone example, the first rigid annular member 15 and the second rigidannular member 16 can have an inner diameter 20 and an outer diameter21. The inner diameter 20 of the first rigid annular member 15 can besubstantially equivalent to the inner diameter 20 of the second rigidannular member 16, Likewise, the outer diameter 21 of the first rigidannular member 15 can be substantially equivalent to the outer diameter21 of the second annular planar member 16. Advantageously, thebi-directional non-linear spring member 5 disclosed can provide lowstiffness for low excitations (i.e., small variations in movement of thevehicle, etc.), which can function to isolate high frequency noise. Italso can provide high stiffness for large excitations, which limitsdisplacement of an accompanied device subjected to vibration, such asvehicle launch loads and/or landing loads. Reference is made herein tofirst and second rigid annular members 15, 16 that enclose a portion ofa compliant member 10. It is understood that the first and second rigidannular members 15, 16 can be separated by the compliant member 10 orthey may form two sides of a unitary rigid annular member that enclosesa portion of the compliant member 10.

In accordance with one example, the ci-directional spring device 5 canbe secured to a vehicle by coupling at least a portion of the first andsecond rigid annular members 15, 16 to a portion of the vehicle, leavingthe compliant member 10 unencumbered and free to move. A sensor, orother device, can be placed/secured on the center portion 13 of thecompliant member 10. When the vehicle moves in a direction “A” that isperpendicular to a face of the compliant member 10 or movement of thevehicle or operation of components of the vehicle induce movement of therigid annular members 15, 16, the compliant member 10 will flex in adirection opposite the direction of travel of the vehicle or oppositethe direction of the movement induced on the rigid annular members 15,16. The flexing action absorbs and/or damps vibrational forces (or otherforces) acting on the sensor (or other device) disposed about the centerportion 13 of compliant member 10 or otherwise supported by thecompliant member 10. The compliant member 10 will resist flexure as afunction of the thickness of the compliant member 10, the applied force,and the overall surface area of the compliant member 10 that is notdisposed within the first and second rigid annular members 15, 16.

In accordance with one aspect, the compliant member 10 can be disposedbetween the first rigid annular member 15 and the second rigid annularmember 16, wherein the center 13 of the compliant member 10, the firstrigid annular member 15, and the second rigid annular member 16 arecollinear. An imaginary axis A through the center portion 13 of thecompliant member 10, the first rigid annular member 15, and the secondrigid annular member 16 is perpendicular to the face of the compliantmember 10. While specific reference is made to rigid annular members, itis understood that the outer perimeter of the annular members 15, 16,may be oval, or other-shaped so long as the inner perimeter is circularin order to evenly distribute bending stresses on the compliant member10. Likewise, the compliant member 10 need not be entirely circular, solong as the compliant member 10 that is subjected to bending stresses iscircular in order to evenly distribute those bending stresses about thedevice.

In one aspect, the compliant member 10 can comprise a thickness lessthan the thickness of the first and second rigid annular members 15, 16.The relative thicknesses of the compliant member 10 can depend on therelative resistance to movement that is desired and the relative levelof vibration to be absorbed. In one non-limiting example, the compliantmember 10 can comprise a titanium sheet ranging from between 0.10 and0.30 mm, and the rigid annular members 15, 16 can comprise a titaniummaterial ranging from between 2 and 6 mm in thickness. In an additionalaspect, the inner diameter 20 of the rigid annular members 15, 16 canrange from between 25 and 35 mm and an outer diameter 21 of the rigidannular members 15, 16 can range from between 35 and 45 mm. In anotheraspect, the inner diameter 20 of the rigid annular members 15, 16 canrange from between 35 and 45 mm and an outer diameter 21 of the rigidannular members 15, 16 can range from between 45 and 55 mm. However, itis understood that there are numerous variations to the above-referenceddimensions that can be utilized as suits a particular application. Inaddition, while the use of titanium is specifically referenced in thenon-limiting example provided above, it is understood that any number ofmaterials can be used in connection with the invention. Othernon-limiting examples include the use of steel, nickel, and/or metalalloys. In some aspects, non-metals may be used. For example, in anothernon-limiting example, the compliant member 10 can comprise athermo-plastic elastomer, graphite composite, textile, or othercompliant synthetic or organic material. The rigid annular members 15,16 can comprise a thermo-plastic elastomer or rigid polyethylene orother polymeric material as suits a particular application. In addition,while the titanium example above describes the compliant member 10 andthe rigid annular members 15, 16 as being made of the same material, itis understood that the compliant member 10 and the rigid annular members15, 16 can be made of different materials. That is, the dimensions andmaterials used for the respective members can be varied to “tune” thespring to a specific stiffness, displacement, or strength requirement.

In one aspect of the invention, first and second center constraintmembers 17, 18 can be disposed on opposing sides of the compliant member10. The first and second center constraint members 17, 18 can comprisecircular disks having a center or center portion 19 that is collinearwith the center 13 of the compliant member 10 and the first and secondrigid annular members 15, 16. The first and second center constraintmembers 17, 18 can have a thickness that is substantially equivalent tothe thickness of the first and second rigid annular members 15, 16. Inan additional aspect, a face of the first center constraint member 17can be coplanar with a face of the first rigid annular member 15 and aface of the second center constraint member 18 can be coplanar with aface of the second rigid annular member 16. An outer diameter 25 of thefirst and second center constraint members 17, 18 can be less than aninner diameter 20 of the first and second annular members 15, 16. In onenon-limiting example, the outer diameter 25 of the first and secondcenter constraint members 17, 18 can be less than half the innerdiameter 20 of the first and second rigid annular members 15, 16, thoughthe dimensions of the center constraint members 17, 18 will vary basedon specific design criteria for a specific application. For example, ina situation where more flexure of the compliant member 10 is desired,the difference between the outer diameter 25 of the center constraintmembers 17, 18 and the inner diameter 20 of the rigid annular members15, 16 will be greater than where less flexure of the compliant member10 is desired. In one example, the center constraint members 17, 18 cancomprise a material that is equivalent to the material used tomanufacture the rigid annular planar members 15, 16, however, the twocan be made from different materials, as suits a particular application.

Referring generally to FIGS. 1-3 where like numerals may describesimilar features, but as shown in greater detail in FIGS. 4-5, abi-directional spring device 50 is disclosed that can comprise aplurality of compliant members 51, a plurality of rigid annular members52, and a plurality of center constraint members 53 coupled together atadjacent points along the face of adjacent rigid annular members 52 andadjacent center constraint members 53. In one aspect, the spring device50 can comprise a first layer comprising a rigid annular member 52 a anda center constraint member 53 a. A compliant member 51 b can comprisethe second layer. The third layer can be similar to the first layerhaving a rigid annular member 52 c and center constraint member 53 c.The first and third layers can enclose portions of the compliant member51 b or second layer. A fourth layer can comprise another compliantmember 51 d disposed behind the third layer followed by a fifth layer(52 e, 53 e) similar to the first and third layers. A sixth layer cancomprise yet another compliant member 51 f, and a seventh layer yetanother rigid annular member 52 g/center constraint member 53 gcombination. The resulting combination of layers is a bi-directionalspring device 50 with a plurality of coupled concentric diaphragm (orsheet) spring members that are operatively coupled to distribute forcesabout the different diaphragms.

The differences between the relative thicknesses of the compliant member51 and the rigid annular member 52/center constraint member 53combination creates a space 54 between the different compliant members51, such that they are not in contact with one another. Rather, adjacentrigid annular member 52/center constraint member 53 combinations can becoupled together and the relative forces acting on the combinedbi-directional spring device 50 can be transferred through that couplingcontact. That is, force that is applied to a top center constraintmember 53 a, for example, can be transferred through adjacent andcollinear constraint members (53 c, 53 e, 53 g). Because they arecoupled to their attendant compliant members, the force transferredthrough the center constraint members is resisted by the attendantcompliant member coupled to the center constraint members.

In one aspect of the invention, adjacent rigid annular member/centerconstraint member combinations can be coupled by welding, fusing,adhesion or some other permanent means of fixation. In another aspect,however, the combinations can be bolted or screwed together to permitassembly/disassembly of a bi-directional spring member combination usinga different numbers of layers. For example, a user may wish to have aspring device with two concentric compliant members or ten concentriccompliant members coupled together by the rigid annular/centerconstraint member combination. In one aspect, a plurality of apertures55 can be disposed through the rigid annular planar member 52/centerconstraint member 53 combinations and the compliant members 51 to enablea user to couple adjacent layers together through bolting or othersuitable means.

With reference generally to FIGS. 1-5, but as shown in greater detail inFIG. 6, in one aspect, the thickness of the compliant member 51 candecrease generally in a direction from the center portion 13 of thecompliant member 51 and extending outward away from the center portion13 of the compliant member 51. In aspects of the technology, it will bemore beneficial for a variable thickness of the compliant member 51 tobe greater near the center portion 13 where stresses on the spring willbe higher. The thickness of the compliant member 51 can increase at alinear rate 60 or a non-linear rate 61 depending on a particularapplication. In addition, the starting point of the linear 60 ornon-linear 61 variation of the thickness of the compliant member 51 maybe near the center portion 13 of the compliant member 51. However, inone aspect, the beginning point can be near the mid-point 62 of thediameter of the compliant member 51 or at some other point along thediameter of the compliant member 51 as suits a particular application.In another aspect, the thickness of the compliant member 51 can decreasegenerally from the center portion 13 of the compliant member 51extending outward away from the center portion 13 of the compliantmember 51. As with the increase in thickness, the decrease in thethickness may be at a linear 60 or non-linear 61 rate as suits aparticular application.

Further disclosed is a system for minimizing sensor vibrationincorporating a bi-directional spring. The bi-directional spring device50 can be mounted to a vehicle and can comprise a rigid annular member52 having a first thickness and a compliant member 51 disposed withinthe rigid annular member 52 having a second thickness. The thickness ofthe compliant member 51 can be less than the thickness of the rigidannular member 52, which contributes to the compliant behavior of thedevice. A center of the rigid annular member 52 and a center 13 of thecompliant member 51 can be collinear, wherein an imaginary axis Bpassing through the center 13 of the compliant member 51 and the centerof the rigid annular member 52 is substantially perpendicular to a faceof the compliant member 51 and a face of the rigid annular member 52. Asensor can be disposed about the center portion 13 of the compliantmember 51 or atop a center constraint member 53. In one aspect, alongitudinal axis B of the bi-directional spring device 50 can beparallel with a direction of travel of the vehicle or parallel with aforce acting on the bi-directional spring 50 resulting from travel ofthe vehicle or resulting from vibrational forces (such as operation of amotor, for example) acting on the bi-directional spring device 50. Inanother aspect, a longitudinal axis B of the bi-directional springdevice 50 can be perpendicular with a direction of travel of the vehicleor forces resulting from travel of the vehicle, operation of a deviceonboard the vehicle, or other forces acting on the vehicle. Thebi-directional spring member 50 can comprise two center constraintmembers 53 disposed on opposing sides of the compliant member 51. Thethickness of the combined center constraint members 53 can besubstantially equivalent to the thickness of the rigid annular member 52enclosing a portion of compliant member 51, and a face of the rigidannular member 52 can be coplanar with a face of the center constraintmember 53.

In accordance with one aspect of the invention, the bi-directionalspring device 50 can have a first position, wherein when thebi-directional spring device 50 is in an unbiased position, the rigidannular member 52 and center constraint member 53 are coplanar. Whensubjected to a load, the center constraint member 53 can move in adirection perpendicular to a face of the rigid annular member 52 as thecompliant member 51 flexes, placing the bi-directional spring device 50in a second position, wherein the center constraint member 53 is nolonger coplanar with the rigid annular member 52. The spring 50 can havea third position where the center constraint member 53 moves to anopposite side of the rigid annular member 52 as a result of flexure ofthe compliant member 51 in a direction opposite the first direction.Similar to the second position, the third position can also result in anarrangement where the center constraint member 53 is not coplanar withthe rigid annular member 52. The resulting configuration provides forspring flexure in at least two directions having a variable (ornon-linear) spring rate.

The system described herein and attendant bi-directional spring devicesare usable in connection with a method for minimizing vibrational forcesacting on sensors, or other devices used in connection with the spring.In one aspect, the method can comprise using a vehicle having abi-directional spring device 50 disposed on the vehicle. Thebi-directional spring device 50 can carry a sensor disposed about acenter of the bi-directional spring device 50 or can be coupled to aplatform for carrying the sensor. The bi-directional spring device 50can comprise a rigid annular member 52 and a compliant member 51disposed within the rigid annular member 52, wherein the thickness ofthe compliant member 51 is less than the thickness of the rigid annularmember 52. An imaginary axis B passes through the center of the rigidannular member 52 and compliant member 51. Movement of the vehicle(e.g., through rapid acceleration, rapid deceleration, or rapid changesin direction), or operation of a device on board the vehicle can createa load on the bi-directional spring device 50. This may be generated bymoving the vehicle in a direction that is parallel with the imaginaryaxis B passing through the center portion 13 of the compliant member 51and/or inducing vibrational forces acting on the bi-directional springdevice 50 in that direction. In one aspect, the direction of rapidchange is away from a position of the sensor and is opposite a directionof linear momentum of the sensor. For example, in an instance where thevehicle is at rest and the momentum of the sensor is zero, a rapidacceleration of the vehicle will result in a gravitational force beingexerted on the sensor due to the rapid change in the momentum of thesensor. Where that rapid change is in the direction that isperpendicular to the face of the bi-directional spring 50, resultingvibrational forces acting on the sensor are minimized through flexure ofthe bi-directional spring device 50. Because the spring isbi-directional, forces resulting from rapid deceleration can be likewiseaccounted for. In one aspect, broadly speaking, when the bi-directionalspring device 50 is used in connection with a linear spring, thetechnology can be used in a method of minimizing and isolatingvibrational forces acting on a payload. The method comprises operating avehicle having a bi-directional spring system disposed on the vehicle,the bi-directional spring system carrying a payload supported by thespring system. As noted herein, the bi-directional spring systemcomprises a non-linear bi-directional spring member coupled to a linearbi-directional spring member such that the spring rate of the non-linearspring is lower than the spring rate of the linear spring when displaceda first amount, the first amount being less than the total spring traveland higher than the spring rate of the linear spring when the combinedspring is displaced a second amount, the second amount being greaterthan the first amount. A load is created on the bi-directional springsystem by moving the vehicle or operating a device disposed about thevehicle and inducing a vibration force on the payload. In one aspect,the configuration of the linear and non-linear spring with a supportedpayload has a resonant frequency that is low for small displacements,providing high attenuation of transmitted vibrations, and high for largedisplacements, limiting displacement during high acceleration events,and reducing dynamic coupling with lower resonant frequency structuralmodes elsewhere in the system to which the payload is coupled, thosecomponents of the system having lower resonant frequency structures.

While specific reference has been made to forces resulting fromacceleration and deceleration, in one aspect of the technology, thebi-directional spring device 50 is also used to attenuate vibrationalforces (e.g., harmonic motion) resulting from general movement of thevehicle rather than non-harmonic motion or vibrational forces resultingfrom operation of a machine coupled to or carried by the vehicle.Moreover, while specific reference is made herein to a sensor, it isunderstood that other devices housed on the vehicle that one may wish toisolate from vibrational forces during movement of the vehicle arecontemplated for use herein.

In addition to the flexure of the compliant member 51 in direction B asshown in FIG. 6, the compliant member 51 may flex in a quasi-“pitch” or“yaw” orientation. That is, flexure of the compliant member 51 in lineardirection B through a center of mass 64 (i.e., in the y-axis) may occur.However, during a vibrational event, a sensor or other member supportedby center constraint member 53 may induce a rotational moment forceacting on the center constraint member 53 about the center of mass 64through the x-axis (shown at “C”) or z-axis (shown at “D”). Theresulting rotational moment force is resisted in a bi-directional modedue to the flexure of the compliant member 51 in opposite directions onopposing sides of the center constraint member 53. For example, if astrut or other member is supported by center constraint member 53 and aforce acting on a top, unsupported component of the strut causes thestrut to tilt or move in a direction that is perpendicular to direction“B,” a rotational force about the x-axis in the direction “C” would bemitigated by a downward flexure of the compliant member 51 on one sideof the center constraint member 53 and an upward flexure of thecompliant member 51 on the opposing side of the center constraint member53. When used in connection with other aspects of the technology (e.g.,the spring combination 110), the arrangement provides for pivoting ofthe center constraint member 53 (and any structures coupled thereto)with respect to the rigid annular member 52.

Reference has been made to annular members for use in connection withthe non-linear spring. It is understood that other geometries may beused without departing from the innovation of the present technology.For example, with reference generally to FIG. 14, a spring 250 isdisclosed comprising a rigid outer member 252, a compliant member 251,and a center constraint member 253. Either the outer member 252 or thecenter constraint member 253 may be affixed to a vehicle or other devicethat is subject to vibrational forces. The arrangement takes advantageof the non-linear displacement and stiffness behavior of the compliantmember 251 when loaded normal to the plane of the flexure of thecompliant member 251. Top and bottom portions 254, 255, of the centerconstraint member 253 are coplanar with top and bottom portions 256, 257of the rigid outer member 252 in one aspect of the technology, thoughsuch an arrangement is not required. As with the spring member 50, thespring member 250 can have a first position, wherein when the spring 250is in an unbiased position. When subjected to a load, the centerconstraint member 253 can move in a direction perpendicular to a face ofthe rigid outer member 252 as the compliant member 251 flexes, placingthe spring 250 in a second position, wherein the center constraintmember 253 is displaced with respect to the rigid outer member 252. Thespring 250 can have a third position where the center constraint member253 moves to an opposite side of the rigid outer member 252 as a resultof flexure of the compliant member 251 in a direction opposite the firstdirection. The resulting configuration provides for spring flexure in atleast two directions having a variable (or non-linear) spring rate.While a single spring 250 is shown in FIG. 14, it is understood that aplurality of spring members stacked on top of one another coupled at thecenter constraint member 253 and rigid outer members 252 may also beused (see, e.g., the stacked annular arrangement shown in FIG. 5).

With reference generally to FIGS. 1-5 and more specifically to FIGS.7-9, it is understood that in one non-limiting example, the rigidannular member 52 can be fixed with relation to an accompanying vehicle(e.g., a rocket, airplane, automobile, etc.) and flexure of thebi-directional spring device 50 occurs through movement at the centerportion 13 of the compliant member 51 relative to movement of thevehicle or forces acting on the bi-directional spring device 50resulting from movement of the vehicle. It is understood, however, thatthe center portion 13 of the compliant member 51 or center constraintmembers 53 can be fixed to the vehicle, or other apparatus (see e.g.,hexapod structure 116 and/or payload 117), and flexure of thebi-directional spring device 50 may occur as a result of movement of therigid annular members 52 relative to movement of the vehicle orapparatus, forces created by movement of the vehicle, operation ofdevices housed on the vehicle, or other external forces. Also, whilespecific reference is made to a vehicle herein, it is understood thatthe bi-directional spring device 50 can be used in any number ofapplications where a bi-directional spring is desirable, including, butwithout limitation, in any instance where the attenuation of avibrational force is desired.

In accordance with one aspect of the technology, a bi-directionaldual-rate spring 110 is disclosed comprising a linear spring 90co-axially coupled to a non-linear spring 100 at the center of thespring 90 by clamp 95. In one aspect, an outer diameter of the linearspring (e.g., a coil spring) 90 is substantially equivalent to an innerdiameter of the outer constraint member 101 of the non-linear spring100. The non-linear spring 100 is similar to the bi-directional springdevice 50 referenced herein comprising at least a compliant planarmember 102 constrained about its outer periphery in some manner therebypermitting flexure of the compliant member 102 to absorb a load (e.g.,vibrations, etc.) placed thereon.

In one aspect, the linear spring 90 can be coupled to a fixed length oradjustable length rigid strut tube 91 and pivot/flexure leg 92. Theadjustable length rigid strut tube 91 can comprise a plurality of nestedrigid tubes that extend about a common axis and have a compressionfitting or other device disposed about distal ends of the strut tube 91to secure the extended (or non-extended) position of the adjustablelength rigid strut tube 91 structure. In one aspect, the pivot/flexureleg 92 comprises a distal end post 93 configured to mate with an openingwithin a strut foot 112. The end post 93 is sized such that it can pivotwithin the opening of the strut foot 112 further minimizing vibrationalforces acting on a load associated with the bi-directional dual-ratespring 110. Advantageously, the compliant members 102 of the non-linearspring 100 can be designed to absorb vibrational forces resulting fromminor changes in vehicle movement (i.e., having a high degree of flexurefrom small movements) while the linear (e.g., coil) spring 90 can bedesigned to absorb vibration forces resulting from larger movementevents (e.g., a missile launch, takeoff or landing of airplane, etc.).While specific reference is made to a linear coil spring 90, it isunderstood that other linear spring members may also be used herein. Forexample, a single helix, double-helix, wave spring, linear torsionalspring, leaf spring, a machine slotted spring, or other spring may beused, and are contemplated for use herein.

In one non-limiting example, the non-linear/linear spring combination(or dual-rate spring) 110 can be used in connection with avibration-isolated platform 115 supported by a plurality of non-linearspring combinations 110 forming a hexapod structure 117. A pair ofnon-linear/linear spring combinations 110 are coupled to thevibration-isolated platform 115 at separate locations on the platform115 and then coupled together to a strut foot 112. Thus, a payload 116disposed atop the isolated platform 115 is subjected to less vibration.The forces acting on the payload 116 can be created by movement of thevehicle or operation of devices associated with the vehicle and, incertain aspects, comprise a variety of different directional forcevectors. In another non-limiting example, the payload 116 itself maycomprise a separate vibrational source. For example, the payload 116 maycomprise a cryogenic cooler, a liquid processor, air filtration system,momentum wheel, control moment gyroscope (CMG), or other device thatgenerates vibration during use. In this instance, the vibrationgenerated from the operation of the payload 116, which is less than thevibrational forces created during an acceleration event, is isolatedfrom the remaining vehicle including, for example, a sensitive on-boardsensor or other electronics. In another example the payload 116 is asensor that requires isolation from vibrational forces generated bycryogenic coolers, liquid processors, etc.

Advantageously, the non-linear/linear spring combination (or springstrut) 110 optimizes attenuation of vibrational forces acting on thepayload 116 during an acceleration event or high amplitude vibrationassociated with movement of the vehicle or operation of a deviceassociated with the vehicle but provides the added benefit of “soft” orlow amplitude vibrational attenuation when the vehicle is at rest butthe payload 116 is creating “soft” or low amplitude vibrational forcesresulting from its operation. In this manner, devices such as launchlocks or bumpers (when used in a rocket application) can be eliminatedfrom the vehicle. However, the vehicle need not be in two differentoperational states to take advantage of the multi-amplitude attenuationcapabilities of the present technology. For example, during a singlevehicle movement event, a payload 116 may experience both high amplitudeand low amplitude vibrational forces at different stages of the vehiclemovement. The present technology provides for an optimized transition ata nominal stage of vehicle (or associated device) operation between useof the linear spring aspect of the technology and the non-linear springaspect of the technology, depending on the resonant frequency ofvibrational forces. In one aspect, a resonant frequency of thebi-directional spring system for a first amount of total springdisplacement is below a resonant frequency of the bi-directional springsystem for a second displacement amount.

Put another way, the combined linear/non-linear spring is configuredsuch that a spring rate of the non-linear spring is lower than thespring rate of the linear spring when displaced a first amount, thefirst amount being less than the total spring travel and higher than thespring rate of the linear spring when the combined spring is displaced asecond amount, the second amount being greater than the first amount. Inone aspect of the technology, the percent of total spring stroke ordisplacement (i.e., the total distance the combined spring travels or isdisplaced in compression or tension) at which the nonlinear and linearspring rates are equal is about ten percent but other percentages ofstroke volume where the rates are equal may be used as suits aparticular application. That effect is that, as opposed to a shock to apayload that is experienced with prior art attenuation devices, thepresent technology provides for a smooth transition between a lowinitial spring rate and higher high-displacement spring rate.

In one aspect, the effective spring rate of the non-linear/linear springcombination 110 can be expressed as the following function:

k=1/(1/k _(L)+1/k _(V))

Where k equals the effective spring rate of the non-linear/linear springcombination (or spring strut) 110, k_(L) equals the constant rate of thelinear spring 90, and k_(V) equals the variable spring rate ofnon-linear spring 100. In other words, the nonlinear spring has a springrate that increases symmetrically (i.e., equally whether it is intension or compression) with displacement. That is, when the nonlinearspring is in a nominal position it has a first spring rate and upondisplacement a predetermined amount (all depending on the springdesign), the non-linear spring will have a second, higher, spring rate.That increase in spring rate is bi-directional and increases equallywhen the spring is in compression or in tension. In one aspect, thelinear spring rate has a constant spring rate between minimum andmaximum rates of the non-linear spring and, in one aspect, is constantwhether the linear spring is in tension or compression.

While specific reference is made herein with respect to a hexapodstructure 116 supported in six degrees of freedom by a plurality ofspring struts 110, it is understood that aspects of the technology maybe used in connection with any number of different structures,including, but without limitation, a tripod, quadrapod, or othermulti-post support structure supporting a payload in any number of aplurality of degrees of freedom. In other aspects, a singlenon-linear/linear spring combination (or spring strut) 110 may be usedas suits a particular application. Moreover, it is understood thatbecause aspects of the technology may be used in a zero-gravityenvironment, the spring strut 110 may be placed on opposing sides of apayload 116 or vibration-isolated platform 115, including top and bottomand/or opposing lateral sides. It is not necessary that thesearrangements only be used in zero-gravity, however. Such use is onlyprovided as an exemplary use of said arrangement.

While specific reference is made herein to an assembly of differentlayers and components that are separately machined and assembled to forma bi-directional spring having a variable spring rate, it is understoodthat in accordance with one aspect of the invention, a bi-directionalspring device can be integrally formed and machined from a singlematerial, That is, the individual components can be separatelymanufactured and later assembled as described more fully above, ormachined, molded, or otherwise created as a single integrated unit outof a single piece of material. Generally speaking, in one aspect of thetechnology, a spring with a variable (or non-linear) spring rate ismachined or formed in a manner that achieves similar non-linear (i.e.,increased rate with increased displacement) spring rate in at least twodirections. The form of the spring comprises a series of collinearplanar annular regions connected by thicker (and hence more rigid)regions alternatively at the inner diameter and outer diameter of theplanar annular regions having a uniform thickness. A cylindrical lumenis formed through the center of adjacent planar annular regions. Thisarrangement allows the thinner planar annular regions to flex while thethick regions remain rigid ensuring the same spring rate in both tensionand compression. The plurality of planar annular regions coupled atalternating interior and exterior points by a plurality of rigidconstraints results in a first spring rate when the spring is displacedgreater than a first predetermined difference and a second spring rate(which is greater than the first spring rate) when displaced greaterthan a second predetermined distances. The first spring rate is the samewhether the spring is in compression or tension. Likewise, the secondspring rate is the same whether the spring is in compression or tension.

In accordance with one aspect of the technology, with referencegenerally to FIGS. 12-13, a bi-directional spring device 150 is shownthat comprises an integrated unit that is generally cylindrical innature having a plurality of rigid center constraints 153. Compliantdiaphragm members 151 (i.e., the annular planar members or planarannular regions) are integrally formed with the rigid center constraints153 at an inner diameter of the compliant diaphragm members 151 andterminate at an outer edge 152 at the outer diameter of the compliantdiaphragm members 151. The rigid center constraints 153 and outer edge152 are thicker than the compliant diaphragm members 151. As such, whena force is applied to the rigid center constraints 153, the thinnerannular planar regions 151 flex. The bi-directional spring device 150can comprise alternating cylindrical spaces 154 between the walls of thecompliant diaphragm members 151 that permit and also limit flexing ofthe compliant diaphragm members 151 to absorb a load placed on the rigidcenter constraint 153. The alternating spaces formed between adjacentannular planar members comprise a closed end and an open end, whereinthe closed end is defined by the inner center constraints and the openend is defined by the opposing outer edges. Additionally, the spacescomprise a closed end and an open end, wherein the closed end is definedby the outer edge and the open end is defined by opposing centerconstraints. The spaces can be configured to be conical (See FIG. 13) tofacilitate bi-directional symmetric spring rates.

In one aspect of the technology, the outer edge 152 is relativelystationary with respect to the remainder of the spring device 150. Thatis, the outer edge 152 moves significantly less in relation to themovement of the rigid center constraints 153. In one aspect, ends A andB of spring device 150 are fixed to a portion of a vehicle, payload, orother device capable of creating a vibrational force. As vibrationalforces are transmitted to the spring member 150 at ends A and/or B, therigid center constraints 153 are compressed or extended based on flexureof compliant diaphragm members 151 resulting in attenuation ofvibrational forces. In one aspect of the technology, a single springsection 160 a may be machined and then welded (or otherwise secured) toa plurality of other machined spring sections in series to create alarger spring. Alternatively, a plurality of spring sections may bemachined from a single piece of material.

In one aspect of the technology, as shown more fully in FIG. 11, thediaphragm members 151 have a uniform thickness and terminate at therigid center constraint 153. As shown in FIGS. 11-13, a fillet orcurvilinear arrangement 155 may be disposed about the internal cornersof unitary spring 150. Rather than angular corners like those shown inFIG. 10, the fillet 155 reduces peak stresses on the corners of theunitary spring 150 during operation. In another aspect of thetechnology, however, as shown more fully in FIGS. 12 and 13 at 156, thediaphragm 151 thickness may vary as the diaphragm extends laterally fromthe rigid center constraint 153 (i.e., the inner diameter of the annularplanar region or compliant diaphragm member 151) to the outer edge 152(i.e., the outer diameter of the annular planar region or diaphragm151). In one aspect, the thickness of the annular planar regiondecreases as the compliant diaphragm member 151 extends laterallyoutward from the rigid center constraint 153 (or inner diameter) to theouter edge 152 (or outer diameter) to reduce peak stresses on the spring150 nearer the outer diameter of the annular planar region.Alternatively, in another aspect, the compliant diaphragm member 151thickness increases as it extends laterally from the rigid centerconstraint 153 to the outer edge 152 as suits a particular applicationwhere a reduction of peak stresses near the rigid center constraint 153is desirable. Depending on where the load is placed on the spring 150,the relative variable thinning of the compliant diaphragm member 151results in a reduction of peak stresses on the spring 150. In oneaspect, the thickness of the compliant diaphragm member 151 increases ina direction away from a longitudinal axis of the spring at a linear ornon-linear rate. In another aspect, the thickness of the compliantdiaphragm member 151 decreases in a direction away from a longitudinalaxis of the spring at a linear or non-linear rate.

In one aspect of the technology, the unitary spring 150 is combined witha linear spring such as that shown in FIG. 7. In other words, theunitary spring 150 may be substituted for the non-linear spring 100 inthe linear/non-linear spring combination (or spring strut) 110 shown inFIG. 7 and used in a manner similar to that shown and described above.While the unitary spring 150 may be machined, it can also be injectionmolded, compression molded, blow molded, vacuum formed, or extrusionmolded. Components of the non-linear spring 100 may likewise bemanufactured. In one aspect the unitary spring 150 and the non-linearspring 100 are manufactured from the same type of material. However, inan alternative arrangement, the two springs are manufactured from adifferent type of material.

With reference now to FIG. 13, a unitary spring 160 is shown having aplurality of annular planar regions 161 coupled at alternative innerdiameters 162 (i.e., center constraint) and outer diameters 163 (i.e.,outer edge). The inner diameters 162 and outer diameters 163 have a wallthickness that is greater than the wall thickness of the annular planarregions 161. Internal corners 165 comprise a fillet or rounded edge. Inthis aspect of the technology, the thickness of the walls of the annularplanar regions 161 are substantially uniform. However, the relativeangle of the walls creates a space 164 between annular walls thatdefines a cone-like shape. In other words, the distance between opposingwalls 161 a, 161 b in one spring segment 160 a, is greater near theinner diameters 162 than the distance between opposing walls near theouter diameters 163. Alternatively, depending on how any particularspring segment is constructed, the opposite arrangement may exist. Thatis, the distance between opposing walls 161 a, 161 b in the springsegment, is smaller near the inner diameters 162 than the distancebetween opposing walls near the outer diameters 163. The end result isan alternating pattern of cone-shaped spring elements. Advantageously,the cone-shaped spring elements result in a net spring rate that issymmetric in both compression and tension. In one aspect, the coneformed by the shape of the walls 161 a, 161 b has a first angle when inan unbiased state resulting in a specific net spring rate. However, inanother aspect, the cone may have a different angle when in an unbiasedstate resulting in a different specific net spring rate due to thedifferent angle of the cone. Regardless, the angle of the cone increaseswhen the spring is displaced in tension and decreases when the spring isdisplaced in compression.

Put another way, the bi-directional linear spring shown in FIGS. 10-13can be described as one or more convolutions revolved about alongitudinal axis. Each convolution has an annular region 151 with afirst thickness connected in series by cylindrical regions 152 having acontinuous second thickness. In one aspect, the thickness of the annularregions 151 is less than the thickness of the cylindrical regions 152.Outer portions of adjacent annular regions are coupled together by afirst cylindrical region and inner portions of adjacent annular regionsare coupled together by a second cylindrical region such that theeffective spring rate of the bi-directional spring increasessymmetrically. That is, it increases at the same rate in compression asit does in tension.

While the foregoing examples are illustrative of the principles of thepresent invention in one or more particular applications, it will beapparent to those of ordinary skill in the art that numerousmodifications in form, usage and details of implementation can be madewithout the exercise of inventive faculty, and without departing fromthe principles and concepts of the invention. Accordingly, it is notintended that the invention be limited, except as by the claims setforth below.

What is claimed is:
 1. A bi-directional nonlinear spring, comprising: aplurality of convolutions revolved about a longitudinal axis each havingan annular region with a first thickness connected in series bycylindrical regions having a second thickness, wherein the firstthickness is less than the second thickness. wherein outer portions ofadjacent annular regions are coupled together by a first cylindricalregion and inner portions of adjacent annular regions are coupledtogether by a second cylindrical region such that the effective springrate of the bi-directional spring device increases symmetrically as itis displaced in either compression or tension.
 2. The bi-directionalnonlinear spring of claim 1, wherein adjacent annular regions areparallel.
 3. The bi-directional nonlinear spring of claim 1, whereinadjacent annular regions form a cone having a cone angle.
 4. Thebi-directional nonlinear spring of claim 3, wherein the cone angleformed by adjacent annular regions is increased when the spring isdisplaced in tension.
 5. The bi-directional spring of claim 1, whereinthe cylindrical regions have a uniform thickness.
 6. The bi-directionalspring of claim 1, wherein the thickness of the annular region increasesin a direction away from a longitudinal axis of the spring.
 7. Thebi-directional spring of claim 6, wherein the thickness of the annularregion increases at a linear rate or a nonlinear rate.
 8. Thebi-directional spring of claim 1, wherein the thickness of the annularregion decreases in a direction away from a longitudinal axis of thespring.
 9. The bi-directional spring of claim 8, wherein the thicknessof the annular region decreases at a linear rate or a nonlinear rate.10. The bi-directional spring of claim 1, wherein the spring comprises aunitary spring machined from a single piece of material or a pluralityof revolved convolutions coupled together to form a series of revolvedconvolutions.